UC Berkeley DUI Study Data Production Documentation

The data pull follows these specifications:

	- Month-census tract aggregated trip counts
	- Covers 2012-07-01 through 2017-01-01
	- Seattle and NYC trips are removed
	- Census tract geos based on 2010 definitions
	- Trip indexing is pegged to May 2015 for census tract 06075061500 located in San Francisco.
	- Indexed data are removed for month-census tracts that fall below .0005.
	- Indexed data are rounded to 7 digits of precision

These fields are generated:

	state - state where the census tract resides
	county - county where the census tract resides
	tract_id - census tract id for which index and trip characteristics are computed based on where the trip began
		format: 2-digit State FIPS, 3-digit County FIPS, then GEOID
	month - month for which index and trip characteristics are computed based on where the trip began
	trip_index_ex_airport - indexed trip count minus trips that started or ended at the airport
	weekend_trip_pct_ex_airport - integer representing the % of non airport trips that began between the hours of Friday 8 PM and Sunday 4 AM
	trip_index_round_flag - flag for if the tract-month falls below .0005
